Hi,
1. Sale of rural agriculture land is not taxable and you can keep the money in NRO account. The definition of rural agricultural land as per income tax act is given below:
Rural agricultural land means an agricultural land in India –
(a) If situated in any area which is comprised within the jurisdiction of a municipality and its population is less than 10,000, or
(b) If situated outside the limits of municipality, then situated at a distance measured-
(i) more than 2 kms, from local limits of municipality and which has a population of more than 10,000 but not exceeding 1,00,000; or
(ii) more than 6 kms, from local limits of municipality and which has a population of more than 1,00,000 but not exceeding 10,00,000; or
(iii) more than 8 kms, from local limits of municipality and which has a population of more than 10,00,000.
2.Yes, exemption u/s 54EC would be available.
You can invest the capital gains of up to INR 50 lakhs in bonds of NHAI or REC, within six months from the date of sale.
Interest received on bonds shall be taxable.
3.Yes, if he has valid power of attorney.